PROJECT ABSTRACT Physical inactivity in children is a major public health risk factor and national health objective. Ethnic-minorities and low income children engage in less physical activity and experience an increased risk of cardiovascular disease. Thus, promoting health-enhancing and sustainable physical activity levels across childhood and adolescence contributes to their health later as adults. There is a need for pediatric physical activity interventions to address the developmental processes (i.e., motor development and psychological constructs including perceived competence) in young children as these factors are established correlates of physical activity. This study will investigate the immediate and long-term effects of a motor skills - the Child Health and Motor Program (CHAMP) on motor competence, perceived motor competence, and physical activity in preschool-age children. The long-term goal of our work is to provide evidence-based intervention strategies to promote positive trajectories of health in children. The specific aims are to: 1) examine the immediate post-intervention effect of CHAMP (compared to control participants) on motor competence, perceived motor competence, and physical activity in preschool-age children; 2) assess the sustainable effect of CHAMP (compared to control participants) on motor competence, perceived motor competence, and physical activity across middle childhood; and 3) examine and compare the immediate and long-term mediating effects of perceived motor competence on the relationship between motor competence and physical activity in preschool-age children. We hypothesize that children in CHAMP, compared to control, will demonstrate higher levels of motor competence, perceived motor competence, and physical activity at post-intervention and across the 3-year follow-up. This study will consist of a cluster randomized control trial and CHAMP will be implemented in a predominantly minority and low income population, Head Start preschoolers (N = 300; 3.5-5 years old). Thirty c lasses of preschool children will be randomly assigned to either the treatment (CHAMP, n = 15) or control (normal preschool free-play/recess, n = 15) condition. The CHAMP intervention will be implemented for 30 minutes/day 4 days per week for 30 weeks. Data will be collected on: a) 7-day physical activity levels using accelerometry, b) process- and product-oriented motor skill competence c) perceived motor competence. Positive findings will support the development of early childhood motor competence and physical activity programs that promote positive and sustainable physical activity behaviors that contribute to healthy growth and development.